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Pharyngeal muscles:Circular
Pharynx is a fibromuscular tube, attached above to the base of the skull and continue below with the oesophagus (end of cricoid at C6). It is about 12 cm in length. It is in communication with the nose, mouth and larynx. It is divided into three parts: nasopharynx, oropharynx and laryngopharynx. Superior/middle/inferior constrictors are thin curved circular sheets of muscles forming the pharynx with three smaller longitudinal muscles, stylopharyngeus, palatopharyneus and salpingopharyngeus. The circular muscles overlap, telescoped into each other like the stacked cups. At the top of the muscles, it is attached to the base of the skull (pharyngeal tubercle anterior to foramen magnum) via the pharyngobasilar fascia. This fibrous thickening of submucosa feels in the gap between the skull and the upper border of the superior constrictor. Nerve innervation: * vagus nerve (cranial nerve X), specifically, by branches from the pharyngeal plexus and by neuronal branches from the recurrent laryngeal nerve Arterial supply of the pharynx * From facial artery (ascending pharyngeal, ascending palatine and tonsillar) * From maxillary artery (greater palatine and pharyngeal) * Linguinal * Superior and inferior laryngeal arteries Venous drainage: * pharyngeal plexuses at the back of the middle constrictor and drain into internal vein and connect with pterygoid plexuses Lymph drainage: * retropharyngeal lymph nodes and then to upper and lower cervical groups * tonsil drain to tonsilar node and then deep cervical groups The superior pharyngeal constrictor muscle sweeps from its origin on the pterygomandibular raphe around the pharynx, diverging and meeting in the midline. origin - pterygoid hamulus, to pterygomandibular raphe and mandible (just above mylohyoid line) insertion - pharyngeal raphe (into the pharyngeal tubercle) Arterial supply: ascending pharyngeal artery, branch of the external carotid artery Nerve: external laryngeal branch of the vagus nerve Gap above the superior constrictor allows eustachean tube, ascending palatine artery and levator palatini to pass. Gap laterally between the superior and middle constrictor (gateway to the mouth), passes the stylopharyngeus and styloglossus and glossopharyngeal and lingual nerves, hypoglossal nerve, lingual artery. The middle pharyngeal constrictor is a fan-shaped muscle located in the neck. The fibres diverge upwards and downwards as they sweep back around the pharynx to enclose the super constrictor and meet in the median raphe. The lower fibres, arch down as far as the vocal folds and lie within the inferior constrictor. Origin: lesser, greater horn of the hyoid bone, the stylohyoid ligament. Insertion: median raphe (blending with the contralateral constrictor fibres). The gap between middle and inferior constrictors is closed by the thyrohyoid membrane, and piercing this membrane are the internal laryngeal nerve and superior laryngeal vessels. The Inferior pharyngeal constrictor, the most inferior of the three constrictors. It passes from the thyroid and cricoid, and the fibres spread backwards into the fibrous pharyngeal raphe. Inferior fibers are horizontal and continuous with the circular fibers of the esophagus; the rest ascend, increasing in obliquity, and overlap with the middle constrictor. The muscle is composed of two parts. The superior thyropharyngeal part * origin: it arises from the oblique line on the side of the lamina, from the surface behind this nearly as far as the posterior border and from the inferior cornu. * insertion: midline pharyngeal raphe The inferior cricopharyngeal part * origin: it arises in the interval between the cricothyroid in front, and the articular facet for the inferior cornu of the thyroid cartilage behind. * insertion: midline pharyngeal raphe Between the thyropharyngeus and cricopharyngeus is a weak area called Killian's dehiscence which a pouch of mucosa can protrude to form a pharyngeal diverticulum. The recurrent and inferior laryngeal nerve pass deep to the lower border of the inferior constrictor.